COORDINATED DESIGN OF GENERATOR EXCITATION AND FACTS FOR TRANSIENT STABILITY ENHANCEMENT

The transient stability of a long transmission system can be significantly influenced by the action of excitation systems and FACTS controls installed. This paper presents a nonlinear coordinated control scheme for excitation systems and TCSC and SVC controls for improving the first swing stability and damping quickly the subsequent power oscillation of a transmission system, where a power plant is connected with a power grid through long transmission line. When TCSC is blocked during fault-on, SVC is then treated as the supplement of the TCSC; after clearance of fault, TCSC is inserted instantly. Thus TCSC, SVC and generator excitation system are all contributed to the enhancement of transient stability simultaneously. The proposed coordination scheme is developed upon nonlinear optimal-variable-aim strategy(OVAS). With two pre-selected aims to be achieved during first swings following a fault and in subsequent dynamic ranges, the first is that the excitation system and FACTS installations are of the maximum outputs, to ensure its maximum transient stability region; then, as the slip of generator approaches zero, coordinated control aim is changed to damp the power oscillation and to drive the system to its steady state. The effectiveness of the proposed control scheme is demonstrated with the Yangcheng-Huaiyin transmission project of China, where the simulations are carried out by the NETOMAC program system. In comparison with a conventional PID design scheme, significant improvements in dynamic performance of the test system are achieved.